Apparatus for fusing contacts onto semiconductive bodies



April 11, 1961 L. PELLEKAAN 2,979,024

APPARATUS FOR FUSING CONTACTS ONTO SEMICONDUC'I'IVE BODIES Filed Aug. 8, 1958 INVENTOR LE EN DERT PELLEKAAN BY J i" j u-ra, K

AGENT APPARATUS FGR FUSENG CQNTACTS ONTO SElVIiCONDUCTIVE BODIES Leendert Pellelraan, Eindhoven, Netherlands, assiguor to North American Philips Company, Inc, New York, N.Y., a corporation of Delaware Filed Aug. 8, 1958, Ser. No. 754,088

Claims priority, application Netherlands Aug. 8, 1957 2 Claims. (Cl. 118--500) The present invention relates to apparatus for fusing contacts onto semi-conductive devices, more especially but not exclusively for making transistors, crystal diodes and similar semi-conducting bodies.

For this purpose, it is customary to employ a device hereinafter briefly termed alloy jig, consisting of graphite, in which one or more cavities accommodate as many semi-conductive bodies and which is further provided with one or more apertures accommodating the material for the contacts. Usually, this material is previously formed into pellets having, for example, a diameter of a few tenths of a millimetre. The fusing operation itself is effected by introducing the alloy jig into an oven in which the required heat treatment is carried out. The alloy jigs are usually made from graphite, since this material can be produced with a high degree of purity which is of paramount importance in this technique. It has further been proposed to make the alloy jigs from ceramic material or stainless steel. When using the last mentioned materials it is, however, more difiicult to avoid impurities than when using graphite. However, graphite is coarse-grained relatively to the very small apertures to be made in it. On account of its poor strength, it is moreover necessary for the component parts of the jigs to be made not too small, due to which the composition of the gas is difiicult to control at the zone of fusing.

The present invention has inter alia for its object to obviate these difficulties.

In accordance withthe invention, alloy jigs are employed which comprise mica parts in which apertures are provided for maintaining the contact material in position. It has been found that this mica, if properly cleaned, for instance by washing in trichloraethylene, does not give oif impurities, while as a result of its thinness it does not practically impede a satisfactory circulation of gases at the fusing zone. Also, it does not show any tendency to be wetted by the customary alloys.

In order that the invention may be readily carried into efiect, an example will now be described in detail with reference to the accompanying drawing, which is a sectional view of an alloy jig on an exaggerated scale.

Patented Apr. 11, 1961 A graphite or chrome-iron plate 1 has a cavity 2 accommodating a semi-conductive body 3, for example a slice of n-conductivity type germanium. The plate 1 can. lies a mica plate 4 with two apertures 5 accommodating two globules 6 consisting of contact material, for example indium. The parts 1 and 4 are clamped together by means of springs 7, made of steel. After thus having been filled, the alloy jig is introduced into an oven. The alloying is carried out in a usual protective atmosphere, i.e. hydrogen at a temperature of about 500 C. Mica of a normal grade will withstand temperatures up to about 650 C., though better grades might be used to higher temperatures.

It has been found possible to drill or punch holes having a diameter of at a relative spacing of 50,11. in a mica plate 200/l. thick. When using graphite, such dimensions are practically ruled out.

What is claimed is:

1. Apparatus for fusing contact material to impuritysensitive semiconductive bodies, comprising support means for receiving and supporting a semiconductive wafer, and

a thin mica plate arranged parallel to and mounted on said support and overlying and contacting a surface of said water, said mica plate containing two closely-spaced apertures overlying the wafer surface for receiving and positioning a pair of masses of contact material in engagement with the wafer surface for melting in contact with the said water while confined within the said apertures, said apertures having a diameter less than the thickness of the said mica plate and being spaced apart a distance less than the thickness of the said mica plate.

2. Apparatus for fusing contact material to impuritysensitive semiconductive bodies, comprising support means for receiving and supporting a semiconductive wafer, and a thin mica plate having a thickness not greater than 200 microns arranged parallel to and mounted on said support and overlying and contacting a surface of said water, said mica plate containing two closelyespaced apertures overlying the wafer surface for receiving and positioning a pair of masses of contact material in engagement with the wafer surface for melting in contact with the said water while confined within the said apertures, said apertures having a diameter not greater than 200 microns and being spaced apart a distance not greater than 200 microns.

References Cited in the file of this patent UNITED STATES PATENTS 1,670,700 Weed May 22, 1928 2,506,047 Thomas May 2, 1950 2,798,013 Irmler July 2, 1957 2,835,615 Leinfelder May 20, 1958 2,857,296 Farris Oct. 21, 1958 2,858,246 Pearson Oct. 28, 1958 2,879,188 Strull Mar. 24, 1959 UNITED STA-mas PATENT OFFICE ERTIFICATE 0F CORRECTION Patent NO. 2,979,024

April 11, 1961 Leendert Pellekaan Column 1, line 18, for semi-conductor devices semi-conducting bodies? read SEA L) Attest:

ERNEST W. SWIDER DAVID L. LADD Attesting Officer I Commissioner of Patents USCOMM-DC- 

